Large vehicle suspensions generally have air bags whose height must be maintained close to a predetermined height. When extra cargo is loaded on a truck so the air bag height decreases, pressured air from a pressured air source (e.g. at 140 psi) flows into the air bag, whose pressure may vary between about 40 and 70 psi, with varying load. Valves for flowing air into our out of one or more air bags are often referred to as leveling valves. One effective type of valve uses a pivotally-mounted disc that has a polished seal surface that bears against a polished housing surface. A linkage moves when the air bag height changes, to pivot the disc so as to connect pressured air to an air bag. Holes in a disc surface are of a predetermined diameter in order to pass air at a predetermined rate to an air bag. Most of the disc is not used to contain a hole or to seal, and the use of such disc results in a relatively large area on the disc and on the housing surface engaged by the disc, that have to be ground and polished with high precision. An air bag valve that minimized the areas that must be polished with high precision, would be of value.
There have been suggestions to control air bag height using an electronic control, as compared to a mechanical linkage without electronic control. Such electronic control often can more easily operate a valve that slides rather than one that turns. For example, an electrically energized solenoid provides a simple means for moving a valve member, and it generally uses a simpler connection when connected to a sliding shuttle than to a pivoting disc.